Lately I've been hearing a high pitched noise while accelerating. It only happens when I accelerate moderately. If I push the gas harder the noise goes away. I can pretty much control when the noise happens by pushing the gas harder or letting up a little. I haven't noticed any performance issues so I'm not really sure where this is coming from. I don't have an aftermarket cai or anything else

Anybody had a similar issue or know why this is happening? Any help is appreciated

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2003 Ranger XLT 4x4 4.0L